Smoked Salmon Mousse and Cucumber Tea Sandwiches

Place the cucumber slices between layers of paper towels to remove excess moisture.

Place the smoked salmon in a food processor or blender and process until fairly smooth, 45 to 60 seconds, stopping the machine once or twice to scrape down the sides of the bowl. Add the mayonnaise and sour cream and process until the mixture is very smooth, 30 to 45 seconds, adding the chopped dill and pepper during the final few seconds. Stop the machine as needed to scrape down the sides of the bowl. Transfer the salmon mixture to a bowl and nestle it in a larger bowl filled with ice. Cover and refrigerate.

In a chilled bowl, whisk the heavy cream until soft peaks form. Using a rubber spatula, gently fold the whipped cream into the salmon mixture until just blended. Do not overmix or the mousse will be grainy and lose its shape; it should be firm enough to hold its shape when scooped out with a spoon. Nestle the bowl in the ice again and refrigerate.

Preheat a broiler.

Using a pastry brush, lightly brush both sides of the bread slices with the melted butter. Place the slices on a baking sheet and broil, turning once, until golden brown on both sides, about 30 seconds per side.

Place half of the toasts on a work surface and spread about 2 Tbs. of the salmon mousse on each slice. Arrange the cucumber slices, slightly overlapping, on the mousse and press gently. Top each with one of the remaining toasts.

Using a sharp knife, trim the crusts off the sandwiches. Cut the sandwiches diagonally into quarters. Garnish each sandwich with a small dollop of the remaining mousse and a dill sprig. Arrange on a serving platter and serve immediately.